The present invention relates to a method and apparatus for entering graphics, and more particularly to a graphic entering method and apparatus for use in entering graphics employing a tablet.
A numerically controlled machine tool (hereafter referred to as an NC machine tool) is operated in a manner specified by a machining program stored on an NC tape to subject a workpiece to prescribed machining. To create an NC tape for a cutting operation, numerical control information and other machining conditions are punched into a paper tape in accordance with predetermined rules. The numerical control information includes all the data necessary for machining, such as numerical values obtained from a design drawing and relating to the dimensions of the workpiece that is to be machined, feed speed, and the like. When machining the workpiece by means of an NC machine tool, the NC tape which has been prepared is fed into the tape reader of a numerical control device so that the various instructions recorded on the NC tape may be read successively, the numerical control device responds by executing the read instructions to cause the machine tool to machine the workpiece as prescribed. Since considerable time and experience is required to create the information stored on an NC tape, an apparatus for preparing an NC tape automatically has recently been developed and put into practical use. The apparatus includes a graphic display, keyboard and printer and is extremely useful in preparing NC tapes in a simple, accurate and rapid manner. Such an apparatus for automatically preparing NC tapes is equipped with a microcomputer with its internal main memory for storing the NC tape preparation software, or system program.
To create a machining program by means of the above-described apparatus, the prescribed system program is loaded into the main memory, and a so-called "part program" consisting of a group of data specifying the contour of a part, namely the path of a tool for cutting the contour, must be created and entered in accordance with predetermined rules. The preparation of such a part program is troublesome and time-consuming, and can only be accomplished by a programmer having considerable programming skill. With these difficulties in view, there has been a demand for a system capable of entering graphics simply by specifying a plurality of points on such graphics, and attention has turned to a graphic entering apparatus employing a tablet.
Such a graphic entering apparatus using a tablet can easily enter graphics even if the dimensions thereof are unknown. However, where the size of a graphic form or figure on a drawing to be entered is greater than the read-out area of a tablet, the entire figure cannot be entered.